In Star Trek, when was impulse drive developed? There seems to be an inconsistency. Zephram Cochrane first deployed Warp drive in 2061 with the assistance of chemical rockets, as detailed in Star Trek: First Contact. Is there any mention of Impulse drive prior to 2061? In Where No Man Has Gone Before, men had used impulse drive to reach the edge of the galaxy.

I have read non-canon explanations - if a warp drive moves the object by bending space, it would not be able to compensate between the relative velocity of its destination vs the trip origin, or delta v. As a ship traversed the galaxy, the differences in galactic orbital velocities would require significant delta v moving in any direction within the galactic plane (traveling straight "up" or "down" would not result in any direct change). Even returning to Earth 6 months later would result in a delta v of 60 km/sec as the Earth would be on the other side of the Sun heading in the opposite direction. However, I've never heard mention of this concept in Star Trek and the ships just appear to pop into orbit without necessitating an "impulse burn" to enter orbit.

Is there any canon explanation when or even why Impulse engines were developed? Was it developed after warp drive? There seems to be a discontinuity in the story line.

  • possible duplicate of How fast can impulse drive propel a ship? Jun 26, 2013 at 5:45
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    Cochrane invented warp drive in 2063, not 2061.
    – user931
    Jun 26, 2013 at 6:27
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    The why seems quite obvious. You need some decent sub-light drive for when warp is too fast. Warp is mainly for long distance travel but a space ship also needs to go short distances now and then. What good would be a car that can only drive 200 km/h or more? It's alright for the highway but you can't drive around town like this. A spaceship also needs something for shorter distances or more precise maneuvers. Given the large distances in space even on a comparatively small scale, you still want to go quite fast. There you go -> Impulse Drive. Jun 26, 2013 at 11:39
  • @Sebastian_H I think that's worth an answer.
    – Anthony
    Jun 26, 2013 at 11:59
  • @anthony-arnold Well, he's specifically asking for a canon answer and my comment has nothing to do with canon. In fact, I was rather trying to point out that you don't need a canon answer (at least in my opinion) because it's just logical why they need it. He's also more interested in the chronological order. Jun 26, 2013 at 12:32

3 Answers 3


Impulse and Warp drives do different things. Your non-canon answer is a canon one. Throughout Next Generation Impulse is used to change direction and momentum, which is what is meant by delta-v.

Warp drive does not alter your velocity or momentum, it moves the space around the ship. So once you are out of warp you need some means of propulsion. That propulsion began as chemical rockets, which would be called thrusters in ST, presumably extended through ion drives and progressively iterated on until reaching the present day impulse drives that are used in the various series. I would call ion drives the first "impulse" drive. So that would mean impulse was invented in 1959.

Different cultures use different kinds of impulse systems. I believe the Enterprise (in all forms) uses a kind of fusion powered magnetic propulsion.

  • While that may be, are there any examples of starships using impulse engines to adjust orbit upon exiting warp? It seems like they just pop out of warp into orbit without and hard deceleration. Again, is there any canon mention of impulse engine drive development. Incidentally, I do remember Scotty in TOS commenting about ion drive on an alien ship and how "they could teach us a thing or two". Or is there even any mention that Warp drive cannot be used to change direction or momentum? Kirk commanded the Enterprise to "pivot at Warp 2".
    – craig
    Jun 26, 2013 at 21:59
  • @craig As for reference to being unable to change direction, it was mentioned at least once in DS9. I think it was at the end of 2x17, Playing God, whe they have to avoid the Verteron nodes... Or maybe it was VOY episode, where they had to follow a predetermined route blindly? (That one I don't recall enough to find the episode)
    – Izkata
    Jun 27, 2013 at 1:49
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    +1 for 1959 (but I'd say humanity had impulse drives way before that, primitive Galleys effectively use conservation of momentum and thus could be classified as impulse drive technology).
    – bitmask
    Jun 27, 2013 at 8:59
  • @craig There are several. In the movie Star Trek (2011) they drop out of warp in the midst of the rings of Saturn and then use a short burst of impulse to accelerate and thrusters to maneuver. I remember scenes from TNG (please don't ask me for the episodes) where they turn around in Orbit in ORDER to warp away from the planet or drop out of warp, then fly a curve (which makes no sense) and then go to warp again in the opposite direction. Also, the very principal of warp is: it moves the space around the ship not the ship itself. So no, it can't change direction or momentum. Jun 27, 2013 at 12:40
  • Actually, careful tuning of a warp field for sublight speeds (which are theoretically doable - we even see a static warp field in at least one TNG episode) would allow you to remain in position so that local gravity can cancel your accumulated vector.
    – aramis
    Jun 28, 2013 at 20:02

Impulse drive was invented some thousands of years ago by the first man who threw a stone. Impulse is the integral of a force over time and is equivalent to the momentum it confers to whatever it is applied to.
An automobile is an impulse vehicle.

Hence the impulse engine was invented long before space flight. In the case of space flight is is probably any kind of reaction engine, since that is the most natural way to get a force in space. Ram-jet engines have been considered for space ship, that would collect reaction mass by gathering atoms and ions with a large force field and get momentum by accelerating it with an internal energy source. As for ram-jets in airplanes, the faster you go and the more reactive mass you get.

Impulse engine means engine working with classical Newton-Eistein physics in normal space.

  • So what is wrong with this answer, other than the stupidity of downvoting without telling why ?
    – babou
    May 4, 2014 at 17:31
  • This was what I always assumed impulse drive to mean.
    – Blackwood
    Feb 9, 2017 at 18:46
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    @babou Scientifically, that is what impulse means. But the label and the name "impulse drive" is not the same thing and it means something more specific. Nobody says "impulse drive" to refer to any form of propulsion that exists today - not jet engines or internal combustion engines or throwing rocks - not even the ion drive on the Dawn probe, which bears the closest resemblance to Star Trek's impulse drive. So you probably got downvoted for conflating the general scientific principle with the name.
    – J Doe
    Feb 9, 2017 at 19:32

Zethram Cochrane may well have invented and tested the first human Warp Drive (with a little help from the crew of the Enterprise-D) but he certainly didn't invent the Impulse Drive. That honour goes to the Vulcans who then came to Earth as a result of seeing his successful test. As you can see from their smooth orbital insertion and landing, their ship clearly has both Warp and Impulse engines.

Although the Vulcans (at least according to the Trek: Enterprise canon) are very reluctant to share technology, it's pretty clear from the opening of Enterprise that impulse drive was in regular use within 15-20 years of the events of "First Contact" (see the USS Emmette below). This strongly suggests that they shared this technology with us, allowing humanity to replace the dirty and inefficient reaction drives they used before this.

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